The present invention relates to a disc clamping mechanism whereby an optical disc or a magneto-optical disc or the like is held and rotated.
Disc drive devices equipped with head mechanisms for reading information recorded on a disc or writing information to a disc are known in the form of devices for optical discs such as CDs, DVDs and MDs, and for magneto-optical discs.
With disc drive devices, a turntable of a spindle motor, by which a disk is rotationally driven, must be in pressing contact with and hold the disc. Thus, in disc drive devices, a clamper is provided that is in direct contact with the top face of a disc that is placed on the turntable, and a clamping magnet is provided in the center of the turntable of the spindle motor so as to attract the clamper.
For example, in Japanese Patent Laid-Open Publication No. 2000-156007, a device such as shown in FIG. 15 and FIG. 16 is disclosed. FIG. 15 shows the state before the clamper is attached to the turntable, and FIG. 16 shows the state of the clamper being attached to the turntable.
As shown in the drawing, a spindle motor 131 comprises a motor body 132 and a rotary shaft 133, and a turntable 134, on which an optical disc 150 is placed, is mounted in the rotary shaft 133. A placing face 135, on which the optical disc 150 is placed, is formed on the outer circumference of the turntable 134. In the inner circumference of the placing face 135, a disc guide 137, which protrudes toward upwards from the placing face 135, is formed. When the optical disc 150 is placed on the placing face 135, the disc guide 137 is fit in a central hole 151 of the optical disc 150, in order to position the optical disc.
In the inner circumference of the disc guide 137, a recess 138 is formed. In the recess 138, a clamping magnet 139, which attaches a clamper 145, and a yoke 140 for controlling the magnetic resistance of the clamping magnet 139, are disposed. Furthermore, the inner circumference of the disc guide 137 has an insertion hole 141, which is positioned at the approximate center of the turntable 134, and through which the rotary shaft 133 of the spindle motor 131 passes. The rotary shaft 133 of the spindle motor is attached to the insertion hole 141, and the turntable 134 turns together with the rotary shaft 133.
The clamper 145, which holds the turntable 134 together with the optical disc 150, at the approximate center thereof, has a through-hole 146, through which passes a locking protrusion 129, which is provided in a cover 128 that constitutes a portion of a case for an optical disc device.
A locking piece 147 is locked by way of the locking protrusion 129 that is provided in the cover 128 being inserted in the through-hole 146, and by way of a stopper 130 that is mounted on the tip of the locking protrusion 129, thus allowing the clamper 145 to be mounted so as to be mobile with respect to the upper cover 128. On the outer circumference of the locking piece 147, a positioning protrusion 148 is provided for positioning the clamper 145 in relation to the turntable 134. The clamper 145 is positioned in relation to the turntable 134 by way of the positioning protrusion 148 being fit along the circumference of the recess 138, which is provided in the turntable 134. In addition, in the outer circumference of the clamper 145, corresponding to the placing face 135 of the turntable 134, a disc pressing portion 149 is formed that is in direct contact with the optical disc 150 and clamps the optical disc 150 together with the placing face 135.
As shown above, eccentricity during rotation of the optical disc 150 is controlled by way of accurately positioning on the turntable 134 of the clamper 145, so that suitable recording and playback of the optical disc can be performed.
Furthermore, when the clamper 145 is attached to the turntable 134, because the configuration is such that the optical disc 150 is clamped in between the disc pressing portion 149 of the clamper 145 and the placing face 135 of the turntable 134, the optical disc 150 can be held securely by the turntable 134 and clamper 145.
However, although the clamping magnet 139 and yoke 140 are fixed in the recess 138 with adhesive or the like, if, for example, the adhesive strength decreases due to degradation of the adhesive or the like, there is a risk of the clamping magnet 139 coming off and detaching from the turntable due to shocks resulting from the effect of magnetic attraction when a disc is mounted or removed, vibrations due to fast rotation of the spindle motor, or the like. If the clamping magnet 139 is detached from the turntable, with the conventional device above, the clamping magnet 139 attaches to the clamper 145, the optical disc 150 cannot be held by the turntable 134 and clamper 145, and stable disc driving cannot be achieved.